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question about w/kg and VAM estimates

I see these all the time from both doping discussions, and in general "are riders in form" discussions, but there's one thing that's bothered me. How are these measurements valid at all when they do not come with any uncertainty bar?

This has probably been asked before but it's by far my biggest bugbear when I see stuff like "6.55 w/kg (est)" from some Twitter dude or something. I thought you couldn't just put "Est" after your numbers, you had to calculate your uncertainty!
it's an "estimate" because it will never be exact unless they have the riders actual power file and weight. you can calculate power to weight very close just by knowing what the VAM is on a certain climb (VAM is basically 100% accurate if the climbing time was taken correctly), close enough for it to be useful data. ie: it's not going to be way off like by 0.4 w/kg or something. it's probably more like 0.04 or even less, which is very negligible. it's just a ballpark number used to compare it to other historical performances.
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